Proportional solenoid

ABSTRACT

Proportional single and double acting solenoids are disclosed of the type in which a conical pole piece becomes selectively saturated at locations opposite the armature. These solenoids are subject to side loading and the alignment and centering of the armature shaft is achieved by providing the bearing housings and adjacent bases with matching interfitting tapers to reduce or eliminate side loads on the armature shaft by assuring concentricity. The solenoids also have improved heat transfer by the use of a coil form in the shape of a spool or bobbin made of aluminum, in which one of the radial end walls is provided with a channel or groove in which the magnet leads and the external lead-in wires are connected and mechanically protected, so that the full radial surface of the side wall may be used for heat conduction without air gaps. High temperature silicone grease is employed at the interfaces of the coil, the base, the hub, and the case to improve the efficiency of heat transfer.

United States Patent 1191 Hardwick et al.

[ 1 Aug. 19, 1975 PROPORTIONAL SOLENOID Primary ExaminerHarold Broome[75] Inventors: David Hardwick, Dayton; George Attorney, Agent, orFtrm--Btebel, French & Bugg T. Coors, Tipp City, both of Ohio [57]ABSTRACT [73] Asstgnee: Ledex, lnc., Dayton, Ohio Proportional singleand double acting solenoids are Flledi 12, 1974 disclosed of the type inwhich a conical pole piece be- [21] AppL NO: 450,310 comes selectivelysaturated at locations opposite the armature. These solenoids are subect to side loading and the alignment and centering of the armatureshaft U.S. CL is achieved providing the bearing housings and ad- Int-Cl. jacent bases matching tapers to re ld of Search 335/268, 258, 55,duce or eliminate side loads on the armature shaft by 335/262, 263,174/15 310/16 assuring concentricity. The solenoids also have improvedheat transfer by the use of a coil form in the References Clted shape ofa spool or bobbin made of aluminum, in UNITED STATES PATENTS which oneof the radial end walls is provided with a 854,741 5/1907 Hewlett335/256 channel of groove in which the magnet leads and the 33 9 7Ha|b|eib et 1 335 200 external lead-in wires are connected andmechanically 2,093,368 9/1937 Rypinski 335/256 protected, so that thefull radial surface of the side 3,050,663 8/1962 Zipper 335/251 wall maybe used for heat conduction without air gaps. 31335777 2/1966 Hatashim--335/256 High temperature silicone grease is employed at the ik fiinterfaces of the coil, the base, the hub, and the case 1 man 3,735,3025/1973 Eckert 335/262 to Improve the efficlency of heat transfer 7Claims, 9 Drawing Figures p 62 so |Q 6O V j I i I, I 'I I I I 40 20 l42- 4e 22 1e I6 22 U '52 PATENTED AUG] 91975 SEEKU 2 OF 2 FIG-4 -11] 45no w $1 PROPORTIONAL SOLENOID BACKGROUND OF THE INVENTION This inventionrelates to proportional actuators of the general type disclosed inGerman Auslegeschrift 1,270,178 published June 12, 1968, in whichrelatively movable cylindrical and conical members are separated by aconstant air gap and move by an amount which has a proportion to theamount of energy applied to the solenoid coil. As the armature advancesfrom the apex of the cone formed by the pole piece toward the base ofthe cone, the material of the pole piece becomes saturated in the regiondirectly across from the armature. The shape or slope of the force curveproduced by this type of a solenoid is determined by the configurationof the cone, and the amount of energy or linear force produced is afunction of the rate of change of area on the conical member. GermanPatentschrift No. 847,465, cited in Auslegeschrift 1,270,178, showsarrangements by which the shape or slope of the force curve may bemodified by selecting the configuration of the cone, in a single-actingproportional solenoid.

An inherent characteristic of the general type of solenoid or actuatordescribed above is that there can be substantial side loading of thearmature over that which occurs with conventional conical or flat poleconstruction, due to the fact that many of the lines of flux areperpendicular to the line of motion of the armature. Thus, anymisalignment or lack of concentricity of the armature in the hub and/orbase can result in large side loads being placed on the armature by themagnetic field. This places a high stress on the armature supportbearings, induces friction, and causes accelerated wear of the bearings.

Additionally, the construction of commercially suitable solenoids ofthis type requires considerations with respect to optimizing the rate ofheat transfer so that sufficiently high mechanical force can be obtainedfrom a unit of given size, with an allowable rise in temperature.

It is common practice to use a coil spool or bobbin in the simple formof a spool with which the magnet wires are brought out through theoutside surface of one of the end flanges to be connected to the leadwires. Such constructions, however, do not permit the end flanges of thebobbin to be in intimate contact with the adjacent solenoid parts suchas the base or the hub, and the air gaps thus produced result in poorheat transfer. Often, little attention is paid to the further problem ofremovingthe heat from the hub and bases to a remote point or heat sinkfor continuous operation.

A different type of prior single-acting proportioning solenoid is shownin the US. Pat. of Cowan No. 3,725,747 of 1973 in which the armature isshaded to produce high magnetic leakage path and saturation loss. In oneembodiment, an electrical solenoid coil is wound on a metal spool which,itself, forms the bore through which the armature moves. To reducefriction, synthetic buttons or piston rings are mounted on the armatureand engage the inside surface of a metallic spool. In anotherembodiment, the bore is formed by a sleeve of low friction syntheticmaterial. However, the armature of the Cowan type of solenoid is notsubject to unusual non-axial or side-loading due to the fact that thelines of force are primarily maintained parallel to the line of movementof the armature, as in conventional solenoid construction.

SUMMARY OF THE INVENTION An important object of the invention is theprovision of double and single-acting proportional solenoidsincorporating cone-like pole piece members, having an improvedefficiency and a construction for maintenance of concentricity of theparts. Efficiency is enhanced by assuring an optimum rate of heattransfer from the coil forms or bobbins to the adjacent contactingstructures. To this end, the bobbins are preferably formed of high heatconductivity, non-ferrous material, preferably aluminum, although copperor aluminum filled nylon may be used. Where an aluminum bobbin isemployed the surface is preferably hard anodized to provide a dielectricor insulating coating.

From experience, it is known that the maximum coil temperature in asolenoid coil is reached at or near the inside diameter of the coil. Thebobbin design employed in the present invention is one which provides adirect path for this heat to flow off to the base and to the hub of thesolenoid, to minimize temperature rise and to obtain more force.

A further feature of the invention resides in an electric coilconstruction which includes a circumferential channel or groove at theouter surface of one of the bobbin end walls, thus forming a spacewithin which the lead-in wires may be joined to the magnet wire,permitting full and unobstructed surface contact at the end of thebobbin, and thus eliminating the usual air gap, As a further means foreliminating air gaps, high temperature grease, such as silicone grease,is applied to the contacting surfaces of the coil to provide continuityof contact and optimum heat transfer.

The heat transfer efficiency is enhanced by the provision of mountingbrackets which are arranged to receive the heat from the bases as wellas from the hub and transfer it outwardly to a mounting surface, so thatthe heat is removed in a continuous manner. Preferably, the mountingbrackets are made of aluminum and, in the double acting enbodiment, arein direct heat transfer relation to the opposite bases. In the singleacting version, one bracket engages a base while the other bracket is indirect engagement with the hub. In either embodiment, the heat flows outof the coil through paths which are provided by the hub, the bases, andthe cylindrical cases within whichthe coils are received.

- The solenoid is held together by external tie bolts which extendbetween the mounting brackets.

It is also important to maintain a circularly constant air gap betweenthe relatively moving magnetic parts, and to maintain these parts intrue concentric relation to minimize side-loading which would otherwisebe generated by the magnetic field resulting in wear on the bearings,and friction. To this end, the bases in the double acting embodiment areprovided with internal coning and mating tapers come into fullengagement by compressing the gasket material.

This mating taper arrangement and gaskets between the mounting bracketsand bearing housings minimize the chances of cocking of the bearinghousing due to rough handling by assuring full contact between theinterfitted parts The mating tapers also assure that the armature alwaysrides in the center of the clearance openings in the bases.

An important object of the invention is the provision of either doubleor single acting proportional solenoids which are of novel design andwhich particularly assure accurate centering of a movable armature andwhich provide for improved heat dissipation from the coil.

A more particular object of the invention is the provision of animproved coil assembly for solenoids in which there is provided a grooveor recess at one end wall of the bobbin or coil form within which theelectrical connections may-be made, while providing for direct flow ofheat from the end walls of the bobbin into a surrounding structure.

Another particular object of the invention is the provision of asolenoid base and bearing housing provided with mating cone-shapedtapers to assure concentricity.

These and other objects and advantages of the invention will be apparentfrom the following description, the accompanying drawings and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of adouble acting solenoid according to this invention;

FIG. 2 is a longitudinal section through the solenoid of FIG. 1;

FIG. 3 is an exploded perspective view showing the relation of one ofthe bases, the mounting brackets and the adjacent end wall;

FIG. 4 is an elevation, partially in section, of the bobbin or spool;

FIG. 5 is an end elevation of the bobbin of FIG. 4, partially insection, with the sectioned portion looking generally along the line 5-5of FIG. 4;

FIG. 5A is an enlarged fragmentary detail of FIG. 5 showing the magnetwires entering the groove;

FIG. 5B is another enlarged detail of the coil form of the bobbinshowing the lead-in wires entering the groove;

FIG. 6 is a transverse section through a single-acting solenoidaccording to this invention; and,

FIG. 7 is a fragmentary detail of a modification of the armature andpole pieces.

DESCRIPTION OF PREFERRED EMBODIMENTS An embodiment of the invention asapplied to a double-acting proportional solenoid is illustratedgenerally at 10 in FIGS. 1-3. This embodiment includes a pair ofidentical sleeve-like cylindrical cases 12 which are formed offerro-magnetic material. The cases 12 are positioned on axially oppositesides of an annular hub 14. The hub 14 is formed with a central radialbody portion 15 and a pair of axially extending sleeve portions 16. Theinner ends of the cases are in heat transfer abutment with the adjacentradial faces of the body portion 15, as shown in FIG. 2. The hub 14 isalso formed of ferro-magnetic material, and the sleeve portions 16define an armature-receiving bore or opening therethrough.

A pair of identical bases 20 are also formed of ferromagnetic materialand are provided with disc'shaped bodies 21. The bodies 21 have radiallyinwardly-facing surfaces which abut against the outer ends of the casesin heat transfer relation.

Each base terminates in an inner radially-tapered cone-shaped poleportion 22. The pole portion 22 is offset from the body 21 inwardlytoward the adjacent sleeve portion 16 of the hub. The apex 22' of eachof the bases 20 is spaced axially from the adjacent terminal end of asleeve portion 16 by a substantial gap 23 to reduce leakage. Preferably,only the outer surface of the pole portion 22 is tapered, while theinside surface thereof defines a cylindrical opening which hassubstantially the same inside diameter as the opening defined by thesleeve portion 16 of the hub 14, although it is not essential that theseinside diameters be precisely the same.

In the double acting embodiment of the solenoid 10, a pair of identicalelectrical coil assemblies are employed which are positionedsymmetrically on either side of the radial body portion 15 of the hub14. The electrical coil assemblies each includes a generallyspool-shaped coil form or bobbin 30. The bobbins are formed ofnon-magnetic material and have an inside diameter proportioned to bereceived over one of the sleeve portions 16 in the axial space betweenthe radial faces of the base and hub. The construction of the bobbins 30is described in further detail in connection with FIGS. 4 and 5. Anelectrical coil 32 is wound on each bobbin 30 and the outside diameterof the coil is a close fit with the inside diameter of the associatedcase 12.

An axially-extended cylindrical armature 35 is received within thearmature openings formed by the sleeve portions 16 and the pole portion22. The armature is also made of a suitable ferro-magnetic material, andhas a length which is slightly greater than the spaced-apart distancesof the bases as defined by the base portions 22, so that when one end ofthe armature 35 is fully telescoped Within one of the conical baseportions 22, the other end is just entering the opposite base portion atthe apex 22 thereof. The sleeve portions 16 of the hub 14 cooperate withthe armature 35 to provide a long, non-working air gap.

The armature 35 is mounted for axial movement within the solenoid on acentral support shaft 40. The shaft is received within low-frictionbearings 42 mounted in identical combined solenoid end walls and bearinghousings 45. The bearing housings 45 cooperate with the bases 20 in aspecial way to assure concentricity of the armature with respect to thebases. Ideally a radially constant-clearance air gap is maintained aboutthe armature 35 with respect to the bases and the hub, although adifferent clearance may be provided between the armature and the baseson the one hand and between the armature and the hub on the other hand.

To maintain base-to-armature concentricity, the housing 45 is providedwith an inwardly extending portion 46, the outer surface 48 beingdefined by a coneshaped taper which precisely mates with a matchinginside cone-shaped tapered surface formed on each base 20. When thematching surfaces 48 and 50 (FIG. 3) 3) are interfitted, the shaft 40 isheld precisely in concentric relation with respect to the cylindricalopening in the tapered base portion 22. The inter-fitting and matchingtapers defined on each of the bearing housings and bases assure analignment condition which is not subject to being knocked out ofalignment by usage or rough handling. Cushion washers 52 may be placedat the inside faces of the bearing housings to absorb any shock ofcontact by the armature.

When the bases 20 and the housings 45 are interfitted as described,there is an axial clearance space between each bearing housing and itsassociated base. Aluminum mounting brackets 55 are received in thesespaces, and they are provided with a central opening 56 as shown in FIG.3 through which the conical extended portion of the bearing housings 45is received. The brackets 55 are terminated in outwardly turned legs 58forming mounting feet. The bearing housings 45 are assembled to thebrackets 55 by threaded screws 60. A gasket 62 is interposed between theradial inside wall of the housing 45 and the adjacent flat surface ofthe bracket 55. Four tie bolts 65 extend externally of the cases 12 andhub between the opposite mounting brackets to retain the entire assemblyby urging the mounting brackets tightly into abutment with the outsideradial surfaces of the adjacent bases. The brackets 55 thus have optimumdirect surface contact with the bases to receive heat therefrom andconduct the same away to the mounting structure. The gaskets 62 permitthe matching tapers on the base and the bearing housing to fully matewith each other, by compression of the gasket material, when the screws60 are tightened.

As previously mentioned, the invention provides for improved heat flowcharacteristics from the coil 32 and the bobbins 30, and to this end,the bobbins 30 are preferably made of high heat conductive non-ferrousmetal, such as aluminum. The outside radial surface of one end of eachbobbin is in abutment with the adjacent radial surface of the hub 14,and the opposite outside radial surface of the bobbin 30 is in fullabutment with the adjacent inside radial surface of the base 20. Theinside cylindrical surface of the bobbin is formed as a close fit on theoutside of the sleeve portion 16 of the hub 14.

The interfaces between the coil assembly, on the one hand, and betweenthe hub, the base, and the case on the other hand, are coated with ahigh temperature heat-conductive or heat transfer material 70, such as asilicone compounded grease. Such greases are semisolid mixtures ofsilicone fluids and thickeners or inert fillers which have an ability tomaintain their viscosity or consistency over wide temperature rangeswithout melting and running away, smoking, charring or solidifying.Particularly suitable materials for this purpose consist of siliconecompounds G-640 and G-64l of General Electric Company, Silicone ProductsDepartment, Waterford, NY. The compound may also be applied at themutually contacting radial faces of the cases 12 and the hub and bases.The compound 70 thus eliminates any air gaps particularly between thecoil as sembly and the adjacent contacting components to provide forcontinuity and improved heat conductivity.

The heat from each of the bobbins may flow directly to the adjacent base20 through one radial end of the bobbin. Also, additional heat paths areprovided. Thus, the heat may flow directly outwardly to the case 12 andthen through the base to the mounting brackets 55. The radial flatengagement of the ends of the case with the base and hub provide foroptimum heat transfer. Also, since a substantial inner portion of thebobbin is received directly on a sleeve portion 16, a good deal of theheat will be thereby transferred to the hub 14, and the mechanicalconnection between the hub 14 and the adjacent case 12 permits the heatto be transferred from the hub to the case, and again through the baseto the mounting bracket. The heat thus may flow, in the double actingembodiment, in either direction depending upon temperature differential.For example. if one of the two electrical coil assemblies is in use, itis apparent that paths are provided so that the heat may flow therefromin either direction into the opposite mounting brackets, again dependingupon temperature differential.

I The solenoid construction includes a specially formed bobbin as shownin FIGS. 4 and 5, by means of which electrical connections are made tothe coil while maintaining full face contact at both ends thereof. Forthis purpose, the inside radial wall of the bobbin 30 is provided with acircumferential groove or channel 82 to receive the leads of the winding32 and to receive the external power leads 85 and to provide a space forthe electrical connections. Since the channel 82 is formed in the outersurface of the wall 80 it does not adversely affect the conduction ofheat along the bobbin and through the ends thereof, and since theelectrical connections are made within the channel, the lead wires arenot brought out through the bobbin ends, as in conventionalconstruction, which would result in an air gap. Also, the channel 82provides mechanical protection for the lead-in wires and for the magnetwires.

As shown in FIG. 5A, the inside magnet wire 86 is brought into thechannel 82 through an opening 87 extending to the inside surface of thebobbin, and this lead may be dressed along an outwardly tapered wall 88into the groove 82. The outside magnet wire 89 may be brought into thegroove 82 through a shallow cut 90 and turned in the opposite direction.The lead-in wires 85 are shown in FIG. 5B as being brought in at the topof the bobbin adjacent the channel 82, and to turn in oppositedirections and to make electrical connections with the magnet wires 86and 89 entirely within the dimensions of the channel 82. The cases 12are formed with shallow axial slots (FIG. 2) providing access openingsfor the wires 85. The bobbin 30 is preferably hard-anodized over itsentire surface to form an electrical insulation coating.

The invention is applicable to a single-acting solenoid as well as adouble-acting solenoid, by utilizing many of the same parts which havebeen described in connection with FIGS. 2 and 4. However, a modified hub14A is employed which may be formed from the same material as the hub 14except that the sleeve portion 16A extends only in one direction, theremainder of the hub being of constant thickness to provide a lowleakage flux path. However, in this case, the inside taper 50A is formedon the inside of the modified hub 14A to receive the corresponding taper48 of the adjacent bearing housing 45, to assure alignment for the shaft40A. The modified armature 35A carried on the shaft is, of course.shorter as it cooperates only with one base 20. A return spring may bemounted on the extended end of the shaft 40A against the outside surfaceof the housing 45A to resist the movement of the armature 35A, in asingle-acting unit.

A further modification which may be applied to either a single ordouble-acting solenoid version is shown in FIG. 7 in which the conicallytapered portion of the pole is applied in the armature 135 as shown at135A, and in which the base 120 is formed with a non-tapered cylindricalpole portion 136. All other parts may remain as described above.

In the operation of both the single and double-acting solenoids, theelectrical coils may be operated in an open loop condition, or may beoperated in a closed loop using the control circuit disclosed andclaimed in the copending application of Myers, entitled SolenoidServomechanism, Ser. No. 439,324, filed Feb. 4, 1974, and assigned tothe same assignee as this invention.

As the armature advances toward the base of the cone defined by the baseportion 22 in the embodiments of FIGS. 2 and 6, each section of the conesaturates directly across from the armature. The shape or slope of theforce-stroke curve is determined by the angle and slope of the cone, andthe amount of energy produced is a function of the rate of change ofarea in the cone.

It is also important that the ID. of the hub 14 be positioned andmaintained in a concentric relation with respect to the armature 35 andthe bases, to thus provide a constant air gap around the armature. Thismay be accomplished by the assembly of the bases and the hub on aprecision mandrel. The concentric relation of the hub and bases is thenmaintained by the tie bolts 65 which apply a compressive force to thebases 20, this compressive force being transmitted through the cases 12and to the radial portion 15 of the hub 14. The tie bolts 65 firmlyclamp the bases and the hub 14 in the predetermined concentric relation.The bearing housings 45 may be attached or removed by the screws 60without disturbing the assembly of the base, cases and hub.

The cone-shaped matching tapers between the bearing housings and basesof FIGS. 2 and 3, or in the case of the single acting embodiment,between the bearing housing and the hub 14A, assure maintenance of atrue concentricity between the armature and the bases. The gaskets 62assure proper mating of the tapers and absorb the shock of roughhandling or the like as may be applied to the mounting brackets 55. Ifit should be necessary to remove or reassemble the housings 45, they areautomatically aligned into proper concentric relation by reason of themating tapers. An important advantage of the structure described aboveis that the tolerance and concentricity between the LD and the CD. ofthe hub, bases and bearing housings can be libera].

The heat formed in the electrical coils, is generally concentrated aboutthe inside turns of the coil, and the improved bobbin or coil forms ofthis invention thus provide direct paths for this heat to flow from thebobbin, as described. The channels 82 provide mechanical isolation forthe magnet wires and lead-in wires and helps prevent shorting at theconnections. The ends of the spool make direct heat transfer contactwith the adjacent structure. The contact about the bobbin and the coilwith the adjacent structure is enhanced by the use of the hightemperature grease at the contacting surfaces.

While the coil forms or bobbins are shown as having a completelycircumferential channel or groove 82, it will be appreciated thatwire-receiving grooves or channels formed in, or by, one of the endwalls need not extend completely around the wall. In some instances, itmay be desirable to provide channels of only limited arcuate length,sufficient to provide a mechanical recess for the lead-in wires and forthe ends of the magnet wires, and to provide a region within which theelectrical connections may be made. Further, it is preferred to positionthe somewhat wider channel end of the coil form adjacent the hub, whichplaces the thinner opposite end wall of the coil form adjacent the base,thus providing a more direct heat transfer relation between theelectrical coil itself and the base. Also, while the improved electricalcoil assembly has been disclosed in connection with its use in aproportional solenoid, where the solenoid may be operated for a longperiod of time, it is obviously within the scope of the invention to usethe improved coil assembly in conventional solenoids where its heat flowcharacteristics and its mechanical protection for the wires would alsobe of advantage.

Additionally, the proportional solenoid embodiments of the invention maybe useful merely as long-stroke solenoids in conventional applications,where a load is to be moved over a substantial distance and where theusual non-linear force curve of a conventional solenoid is undesirable.

While the forms of apparatus herein described constitute preferredembodiments of the invention, it is to be understood that the-inventionis not limited to these precise forms of apparatus, and that changes maybe made therein without departingfrom the scope of the invention.

What is claimed is:

1. For use with double and single acting solenoids, the combinationcomprising an annular hub having an abutment portion defining a radialwall and a cylindrical sleeve portion, a base axially; spaced from saidhub, means on said base forming an annular pole portion and having meansdefining a second radial wall in axially spaced relation to said hubwall, a cylindrical axially extended armature, meansmounting saidarmature for axial movement within said hub, an electrical coil assemblyincluding a spool-shaped coil form made essentially of high heatconductive material, said coil form having an inside surface received onsaid hub sleeve portion and having radial end faces in respective heattransferring abutment with said hub and base walls, an electrical coilwound on said form, and one end of said coil form having means defininga radially outwardly opening channel proportioned to receive the magnetwire of said coil and to receive the external power leads thereinproviding a space for electrical connection with said coil wires.

2. A proportional solenoid comprising an annular hub having an abutmentportion defining a radial wall, a base axially spaced from said hub,means on said base forming an annular pole portion extending axiallytoment with said hub and base walls, an electrical coil' wound on saidform, said form having means therein defining a circumferentialoutwardly-spacing channel formed in one end of said form andproportioned to receive the magnet wire of said coil and to receive theexternal power leads thereon providing a space for electricalconnections with said coil wires, and high temperature grease at theinterfaces between said coil form and said hub and base to eliminate airgaps and to improve the heat transfer rate from said coil assembly.

3. In proportional solenoids including an armature mounted on anelongated axially extending shaft and further including an annular huband at least one axially spaced annular base surrounding said armature,said base and hub defining a path for movement of said armature, inwhich said armature is subject to sideloading due to magnetic lines offorce between said ar mature and said base, the improvement in shaftmounting and centering means comprising a bearing housing, a bearingpositioned centrally of said housing for supporting one end of saidshaft for axial movement, said bearing housing having a wall portiondefined by an external inwardly-facing annular taper, means on said basedefining an internal outwardly-facing annular taper proportioned to matewith said housing taper, and means joining said bearing housing and saidbase with said tapers in mating relation to maintain a condition ofconcentricity of said armature with respect to said base.

4. The improvement of claim 3 further comprising a second said baseaxially spaced from said one base, and a second said bearing housing inmating relation thereto and having a bearing therein receiving the otherend of said shaft.

5. The improvement of claim 3 further comprising a second said bearinghousing member, means in said hub defining an internal, outwardly-facingtaper proportioned to mate with the external taper on said secondbearing housing, said second bearing housing having a bearing thereinreceiving the other end of said shaft, and means joining said secondhousing to said base with the tapers thereof in mating relation.

6. A double acting proportional solenoid comprising a hub having asymmetrically annular sleeve portion and a generally centrallypositioned radial portion, a pair of electrical coil assemblies mountedon said sleeve portion respectively on opposite axial sides of saidradial portion, a pair of axially-spaced bases having radial bodyportions in abutment with one of said coil assemblies, and each saidbase having an inwardlyextending annular tapered pole portionterminating in an apex spaced from said hub sleeve portion forming anair gap therebetween, a cylindrical armature mounted within said hubhaving opposite ends in interfittin g relation to said pole portions sothat selective energization of either of said coil assemblies willcreate a force tending to urge said armature axially in one direction orthe other with respect to said bases, means on said armature defining anaxially extending shaft, means mounting said armature shaftconcentrically on said bases including .a correspondiing pair of bearinghousings, means on said housings and said bases defining cooperatingmating concentric tapers, and bearings in said housings engaging saidshaft adjacent the ends thereof and supporting said shaft and armaturefor said axial movement.

7. In electric solenoids including an armature on an axially movableshaft and further including a hub and at least one annular basecooperating with said armature to define a circumferential air gaptherebetween, said armature being subject to magnetic side-loading uponthe occurrence of a lack of concentricity between said armature and saidbase, the improvement in shaft mounting and centering comprising abearing housing having means defining a bearing supporting one end ofsaid shaft for axial movement therethrough, said bearing housing havinga wall portion defined by an annular taper formed concentrically of saidshaft, means on said base defining an annular taper proportioned tointerfit and mate with said housing taper, and means joining saidbearing housing and said base with said tapers in interfitted relationto maintain a circumferentially constant air gap between said armatureand said base.

1. For use with double and single acting solenoids, the combinationcomprising an annular hub having an abutment portion defining a radialwall and a cylindrical sleeve portion, a base axially spaced from saidhub, means on said base forming an annular pole portion and having meansdefining a second radial wall in axially spaced relation to said hubwall, a cylindrical axially extended armature, means mounting saidarmature for axial movement within said hub, an electrical coil assemblyincluding a spool-shaped coil form made essentially of high heatconductive material, said coil form having an inside surface received onsaid hub sleeve portion and having radial end faces in respective heattransferring abutment with said hub and base walls, an electrical coilwound on said form, and one end of said coil form having means defininga radially outwardly opening channel proportioned to receive the magnetwire of said coil and to receive the external power leads thereinproviding a space for electrical connection with said coil wires.
 2. Aproportional solenoid comprising an annular hub having an abutmentportion defining a radial wall, a base axially spaced from said hub,means on said base forming an annular pole portion extending axiallytoward said hub and having means defining a second radial wall inaxially spaced relation to said hub wall, a cylindrical axially extendedarmature, means mounting said armature for axial movement within saidhub and base, an electrical coil assembly including a spool-shaped coilform made essentially of high heat conductive material, said coil formhaving an inside surface received in heat transfer relation on said huband having radial end faces in respective heat transferring abutmentwith said hub and base walls, an electrical coil wound on said form,said form having means therein defining a circumferentialoutwardly-spacing channel formed in one end of said form andproportioned to receive the magnet wire of said coil and to receive theexternal power leads thereon providing a space for electricalconnections with said coil wires, and high temperature grease at theinterfaces between said coil form and said hub and base to eliminate airgaps and to improve the heat transfer rate from said coil assembly. 3.In proportional solenoids including an armature mounted on an elongatedaxially extending shaft and further including an annular hub and atleast one axially spaced annular base surrounding said armature, saidbase and hub defining a path for movement of said armature, in whichsaid armature is subject to side-loading due to magnetic lines of forcebetween said armature and said base, the improvement in shaft mountingand centering means comprising a bearing housing, a bearing positionedcentrally of said housing for supporting one end of said shaft for axialmovement, said bearing housing having a wall portion defined by anexternal inwardly-facing annular taper, means on said base defining aninternal outwardly-facing annular taper proportioned to mate with saidhousing taper, and means joining said bearing housing and said base withsaid tapers in mating relation to maintain a condition of concentricityof said armature with respect to said base.
 4. The improvement of claim3 further comprising a second said base axially spaced from said onebase, and a second said bearing housing in mating relation thereto andhaving a bearing therein receiving the other end of said shaft.
 5. Theimprovement of claim 3 further comprising a second said bearing housingmember, means in said hub defining an internal, outwardly-facing taperproportioned to mate with the external taper on said second bearinghousing, said second bearing housing having a bearing therein receivingthe other end of said shaft, and means joining said second housing tosaid base with the tapers thereof in mating relation.
 6. A double actingproportional solenoid comprising a hub having a symmetrically annularsleeve portion and a generally centrally positioned radial portion, apair of electrical coil assemblies mounted on said sleeve portionrespectively on opposite axial sides of said radial portion, a pair ofaxially-spaced bases having radial body portions in abutment with one ofsaid coil assemblies, and each said base having an inwardly-extendingannular tapered pole portion terminating in an apex spaced from said hubsleeve portion forming an air gap therebetween, a cylindrical armaturemounted within said hub having opposite ends in interfitting relation tosaid pole portions so that selective energization of either of said coilassemblies will create a force tending to urge said armature axially inone direction or the other with respect to said bases, means on saidarmature defining an axially extending shaft, means mounting saidarmature shaft concentrically on said Bases including a correspondiingpair of bearing housings, means on said housings and said bases definingcooperating mating concentric tapers, and bearings in said housingsengaging said shaft adjacent the ends thereof and supporting said shaftand armature for said axial movement.
 7. In electric solenoids includingan armature on an axially movable shaft and further including a hub andat least one annular base cooperating with said armature to define acircumferential air gap therebetween, said armature being subject tomagnetic side-loading upon the occurrence of a lack of concentricitybetween said armature and said base, the improvement in shaft mountingand centering comprising a bearing housing having means defining abearing supporting one end of said shaft for axial movementtherethrough, said bearing housing having a wall portion defined by anannular taper formed concentrically of said shaft, means on said basedefining an annular taper proportioned to interfit and mate with saidhousing taper, and means joining said bearing housing and said base withsaid tapers in interfitted relation to maintain a circumferentiallyconstant air gap between said armature and said base.